Methods, compositions, and devices for the occlusion of cavities and passageways

ABSTRACT

Provided herein are methods, compositions, and devices for occluding cavities or passageways in a patient, in particular cavities or passageways in the cardiovascular system of a patient, such as the LAA of a patient&#39;s heart. The methods, compositions, and devices can be used to percutaneously occlude the LAA, decreasing the risk of thromboembolic events associated with AF.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/780,533, filed Mar. 13, 2013, the disclosure of which is expresslyincorporated herein by reference.

FIELD

The present disclosure is generally related to methods, compositions,and devices for occluding cavities or passageways in a patient, inparticular cavities or passageways in the cardiovascular system of apatient, such as the left atrial appendage (LAA) of a patient's heart.

BACKGROUND

Embolic stroke is a leading cause of death and disability among adults.The most common cause of embolic stroke emanating from the heart isthrombus formation due to atrial fibrillation (AF). AF is an arrhythmiaof the heart that results in a rapid and chaotic heartbeat, producingdecreased cardiac output and leading to irregular and turbulent bloodflow in the vascular system.

In the case of patients who exhibit AF and develop an atrial thrombus,clot formation typically occurs in the left atrial appendage (LAA) ofthe patient's heart. The LAA is a small cavity formed within the lateralwall of the left atrium between the mitral valve and the root of theleft pulmonary vein. In normal hearts, the LAA contracts in conjunctionwith the rest of the left atrium during the cardiac cycle; however inthe case of patients suffering from AF, the LAA often fails to contractwith any vigor. As a consequence, blood can stagnate within the LAA,resulting in thrombus formation.

Elimination or containment of thrombus formed within the LAA offers thepotential to significantly reduce the incidence of stroke in patientssuffering from AF. Pharmacological therapies, for example the oral orsystemic administration of anticoagulants such as warfarin, are oftenused to prevent thrombus formation. However, anticoagulant therapy isoften undesirable or unsuccessful due to medication side effects (e.g.,hemorrhage), interactions with foods and other drugs, and lack ofpatient compliance.

Invasive surgical or thorascopic techniques have been used to obliteratethe LAA, however, many patients with AF are not suitable candidates forsuch surgical procedures due to a compromised condition or havingpreviously undergone cardiac surgery. In addition, the perceived risksof surgical procedures often outweigh the potential benefits.

Recently, percutaneous occlusion implants for use in the LAA have beeninvestigated as alternatives to anticoagulant therapy. However, theseimplants are relatively non-conforming. Due to the non-uniform shape ofthe LAA, existing implants cannot completely seal the opening of the LAAin all patients. As a consequence, approximately 15% of patientsreceiving these implants experience incomplete LAA closure,necessitating prolonged treatment with anticoagulants. The anatomy ofthe left atrium and LAA of some patients also precludes the use of suchimplants. In addition, the occlusion implants can also causelife-threatening perforations of the LAA during the placement procedure.

More effective methods of occluding cavities or passageways in apatient, in particular cavities or passageways in the cardiovascularsystem of a patient, such as the LAA, offer the potential to improvepatient outcomes while eliminating the undesirable consequences ofexisting therapies.

SUMMARY

Provided are methods, compositions, and devices for occluding cavitiesor passageways in a patient, in particular cavities or passageways inthe cardiovascular system of a patient, such as the LAA of a patient'sheart. The methods, compositions, and devices can be used to decreasethe rate of thromboembolic events associated with AF by occluding theLAA.

Methods for occluding the LAA of a patient can involve injecting acrosslinkable biomaterial into the LAA of the patient. The crosslinkablebiomaterial can be, for example, a fluid or fluids which can comply withthe irregular shape of the interior of the LAA. Upon injection, thecrosslinkable biomaterial can crosslink in situ in the LAA, forming abiocompatible polymeric matrix. The biocompatible polymeric matrix canfunction as an occlusive body, occupying the void space of the LAAwithout adversely impacting cardiac function.

The crosslinkable biomaterial can be injected into the LAApercutaneously. In some embodiments, the crosslinkable biomaterial canbe percutaneously injected via a delivery catheter. The deliverycatheter can comprise (i) a proximal region; (ii) a distal regioncomprising a distal tip; (iii) at least a first lumen extending from theproximal region to the distal region; and (iv) an occluding elementpositioned in proximity to the distal tip. The delivery catheter canfurther comprise at least a second lumen extending from the proximalregion to the distal region. In some embodiments, the first lumen can befluidly isolated from the second lumen. In other embodiments, the firstlumen and the second lumen are fluidly connected by a mixing channel.

The delivery catheter can be is inserted into the vasculature of thepatient (e.g., into the femoral vein), and advanced through thepatient's vasculature, such that the distal tip of the delivery catheterreaches the patient's left atrium. The distal tip of the deliverycatheter can then be advanced into the LAA, such that the occludingelement of the delivery catheter transitorily occludes the LAA. Acrosslinkable biomaterial can then be injected into the LAA of thepatient via the delivery catheter where it increases in viscosity uponcrosslinking to form a biocompatible polymeric matrix. The crosslinkablebiomaterial as well as the resultant biocompatible polymeric matrix canbe selected to possess suitable materials properties (e.g., viscosity,cohesive strength, adhesive strength, elasticity, degradation rate,swelling behavior, cure time, etc.) for use in occlusion of the LAA.

In some embodiments, the crosslinkable biomaterial comprises amulticomponent composition. For example, the crosslinkable biomaterialcan comprise a first precursor molecule present in a first solution anda second precursor molecule present in a second solution, wherein thefirst precursor molecule is reactive with the second precursor moleculeto form a biocompatible polymeric matrix. In one embodiment, the twosolutions are combined during the course of injection via the deliverycatheter (e.g., by mixing within a mixing channel within the deliverycatheter). In another embodiment, the two solutions are individually(simultaneously or sequentially) injected into the LAA, and combine insitu to form a biocompatible polymeric matrix.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an anterior illustration of a heart, including proximalportions of the great vessels.

FIG. 2 is a schematic drawing illustrating a delivery catheter.

FIGS. 3A-3F are schematic illustrations of mixing channels that can beincorporated into the delivery catheter.

FIG. 4 is a schematic illustration of a patient's heart in partialsection with a delivery catheter positioned within the opening of theLAA.

DETAILED DESCRIPTION

To facilitate understanding of the physiology associated with themethods, compositions, and devices described herein, FIG. 1 illustratesthe anatomy of the human heart (100). Referring to FIG. 1, the heart 100is illustrated to show certain portions including the left ventricle(102), the left atrium (104), the LAA (106), the pulmonary artery (108),the aorta (110), the right ventricle (112), the right atrium (114), andthe right atrial appendage (116). The left atrium is located above theleft ventricle, and is separated from the left ventricle by the mitralvalve (not illustrated). As shown in FIG. 4, the LAA (106) has anirregular finger-like or windsock shape with an opening (120)approximately 1.5 cm in diameter. The LAA is normally in fluidcommunication with the left atrium such that blood flows in and out ofthe LAA as the heart beats.

Provided are methods, compositions, and devices for occluding cavitiesor passageways in a patient, in particular cavities or passageways inthe cardiovascular system of a patient (e.g., the LAA of a patient'sheart). Methods for occluding cavities or passageways in a patient, suchas the LAA, can involve injecting or otherwise introducing acrosslinkable biomaterial into the cavity or passageway. Any suitablebiomaterial can be used. For example, the biomaterial can be acrosslinkable biomaterial which is injected into the cavity orpassageway (e.g., the LAA) in a fluid or gel form, and which crosslinksin situ, increasing in viscosity to form a biocompatible polymericmatrix. In these cases, the biocompatible polymeric matrix can functionas an occlusive body, occupying the void space of the cavity orpassageway. In the case of injection of a crosslinkable biomaterial intothe LAA for purposes of occlusion, the biocompatible polymeric matrixcan function as an occlusive body, occupying the void space of the LAAwithout adversely impacting cardiac function.

In situ formation, as generally used herein, refers to the ability ofprecursor molecules that are substantially uncrosslinked prior to and atthe time of injection into a patient to crosslink by forming covalentand/or non-covalent linkages with each other at the site of injection inthe body of the patient.

The crosslinkable biomaterial as well as the resultant biocompatiblepolymeric matrix can be selected to possess suitable materialsproperties (e.g., viscosity, cohesive strength, adhesive strength,elasticity, degradation rate, swelling behavior, cure time, etc.) foruse in occlusion of a particular cavity or passageway, such as the LAA.

For example, the biocompatible polymeric matrix can exhibit anequilibrium swelling ratio suitable for occlusion of the LAA. Swellingrefers to the uptake of water or biological fluids by the biocompatiblepolymeric matrix. The swelling of the biocompatible polymeric matrix canbe quantified using the equilibrium swelling ratio, defined as the massof the biocompatible polymeric matrix at equilibrium swelling (i.e., thematerials maximum swollen weight) divided by the mass of thebiocompatible polymeric matrix prior to swelling (e.g., immediatelyfollowing curing). In many cases, equilibrium swelling is reached withina relatively short period of time (e.g., within about 24-48 hours).

In some embodiments, the biocompatible polymeric matrix exhibits anequilibrium swelling ratio of less than about 8 (e.g., less than about7.5, less than about 7.0, less than about 6.5, less than about 6.0, lessthan about 5.5, less than about 5.0, less than about 4.5, less thanabout 4.0, less than about 3.5, less than about 3.0, less than about2.5, less than about 2.0, less than about 1.5, less than about 1.0, orless than about 0.5). In some embodiments, the biocompatible polymericmatrix exhibits an equilibrium swelling ratio of greater than 0 (e.g.,greater than about 0.5, greater than about 1.0, greater than about 1.5,greater than about 2.0, greater than about 2.5, greater than about 3.0,greater than about 3.5, greater than about 4.0, greater than about 4.5,greater than about 5.0, greater than about 5.5, greater than about 6.0,greater than about 6.5, greater than about 7.0, or greater than about7.5).

The biocompatible polymeric matrix can exhibit an equilibrium swellingratio ranging from any of the minimum values described above to any ofthe maximum values described above. For example, the biocompatiblepolymeric matrix can exhibit an equilibrium swelling ratio of fromgreater than 0 to about 8.0 (e.g., from about 2.0 to about 8.0, of fromabout 2.5 to about 6.0).

The biocompatible polymeric matrix can have mechanical properties thatare compatible with cardiac function, such that the presence of thebiocompatible polymeric matrix within the LAA does not substantiallyimpede or inhibit cardiac function. For example, the biocompatiblepolymeric matrix can be formed to be at least partially compliant withthe constrictive action of the heart muscle throughout the cardiaccycle. Suitable biocompatible polymeric matrices can have elastic moduliranging from about 0.01 to about 100 kPa.

In some cases, biocompatible polymeric matrix is formed to have anelastic modulus similar to that of cardiac tissue. In some embodiments,the biocompatible polymeric matrix has an elastic modulus greater thanabout 5 kPa (e.g., greater than about 6 kPa, greater than about 7 kPa,greater than about 8 kPa, greater than about 9 kPa, greater than about10 kPa, greater than about 11 kPa, greater than about 12 kPa, greaterthan about 13 kPa, greater than about 14 kPa, greater than about 15 kPa,greater than about 16 kPa, greater than about 17 kPa, greater than about18 kPa, or greater than about 19 kPa. In some embodiments, thebiocompatible polymeric matrix has an elastic modulus of less than about20 kPa (e.g., less than about 19 kPa, less than about 18 kPa, less thanabout 17 kPa, less than about 16 kPa, less than about 15 kPa, less thanabout 14 kPa, less than about 13 kPa, less than about 12 kPa, less thanabout 11 kPa, less than about 10 kPa, less than about 9 kPa, less thanabout 8 kPa, less than about 7 kPa, or less than about 6 kPa).

The biocompatible polymeric matrix can have an elastic modulus rangingfrom any of the minimum values described above to any of the maximumvalues described above. For example, the biocompatible polymeric matrixcan have an elastic modulus of from about 5 kPa to about 20 kPa (e.g.,from about 9 kPa to about 17 kPa, from about 10 kPa to about 15 kPa, orfrom about 8 kPa to about 12 kPa).

The biocompatible polymeric matrix can have a cohesive strength suitablefor occlusion of the LAA. Cohesive strength (also referred to as burststrength) refers to the ability of the biocompatible polymeric matrix toremain intact (i.e., not rupture, tear or crack) when subjected tophysical stresses or environmental conditions. The cohesive strength ofthe biocompatible polymeric matrix can be measured using methods knownin the art, for example, using the standard methods described in ASTMF-2392-04 (standard test for the burst strength of surgical sealants).In some embodiments, the biocompatible polymeric matrix has a cohesivestrength effective such that the biocompatible polymeric matrix remainsintact (e.g., does not fragment or break apart into smaller pieces whichexit the LAA) for a period of time effective to permit the LAA to besealed via endothelialization prior to fragmentation of thebiocompatible polymeric matrix.

The biocompatible polymeric matrix can also have a viscosity whichminimizes migration of biocompatible polymeric matrix out of the LAAfollowing injection. In some embodiments, the biocompatible polymericmatrix has a viscosity of at least 50,000 cP (e.g., at least 60,000 cP,at least 70,000 cP, at least 75,000 cP, at least 80,000 cP, at least90,000 cP, at least 100,000 cP, or more) at body temperature (e.g., at37° C.).

The biocompatible matrix can also be selected such that is it retainedat the site of occlusion (e.g., inside the LAA) by a combination ofadhesion to the tissues at the site of occlusion and mechanicalinteraction with the anatomy at the site of occlusion. For example, thebiocompatible polymeric matrix can have an adhesive strength suitablefor occlusion of the LAA. Adhesive strength refers to the ability of thebiocompatible polymeric matrix to remain attached to the tissues at thesite of administration (e.g., the interior of the LAA) when subjected tophysical stresses or environmental conditions. In some embodiments, thebiocompatible polymeric matrix has an adhesive strength effective suchthat the biocompatible polymeric matrix remains within the LAA (e.g.,does not exit the LAA) for a period of time effective to permit the LAAto be sealed via endothelialization prior to fragmentation of thebiocompatible polymeric matrix. Mechanical forces, governed by acombination of properties which can include the swelling of thebiocompatible polymeric matrix, the local anatomy at the site ofinjection (e.g., the particular 3-dimensional shape of the LAA and/orthe surface texture of the LAA interior), and the friction of thebiocompatible polymeric matrix against tissue at the site of injection,can also contribute to retention of the biocompatible matrix at the siteof injection.

The biocompatible polymeric matrix can be formed from materials whichsupport (i.e., do not inhibit) endothelialization. Endothelializationrefers to the growth and/or proliferation of endothelial cells on asurface, such as the blood-contacting surface, of the biocompatiblepolymeric matrix. These materials can be biodegradable ornon-biodegradable. A biodegradable material is one which decomposesunder normal in vivo physiological conditions into components which canbe metabolized or excreted.

In some cases, the biocompatible polymeric matrix can be biodegradable.When the biocompatible polymeric matrix is biodegradable, thebiocompatible polymeric matrix can have a degradation rate effective topermit the LAA to be sealed via endothelialization prior to erosion ofthe biocompatible polymeric matrix. For example, the biocompatiblepolymeric matrix can have a degradation rate effective to permit the LAAto be sealed via endothelialization prior to erosion of 25% by volume ofthe biocompatible polymeric matrix from the LAA (e.g., prior to erosionof 20% by volume of the biocompatible polymeric matrix from the LAA,prior to erosion of 15% by volume of the biocompatible polymeric matrixfrom the LAA, prior to erosion of 10% by volume of the biocompatiblepolymeric matrix from the LAA, or prior to erosion of 5% by volume ofthe biocompatible polymeric matrix from the LAA).

In some embodiments, the biocompatible polymeric matrix has adegradation rate such that about 70% or less by weight of thebiocompatible polymeric matrix degrades within 90 days of curing, asmeasured using the standard method described in Example 1 (e.g., about60% or less by weight, about 55% or less by weight, about 50% or less byweight, about 45% or less by weight, about 40% or less by weight, orless). In some embodiments, the biocompatible polymeric matrix has adegradation rate such that about 85% or less by weight of thebiocompatible polymeric matrix degrades within 120 days of curing, asmeasured using the standard method described in Example 1 (e.g., about80% or less by weight, about 75% or less by weight, about 70% or less byweight, about 65% or less by weight, about 60% or less by weight, about55% or less by weight, about 50% or less by weight, or less).

In one embodiment, the biocompatible polymeric matrix has a degradationrate such that about 45% or less by weight of the biocompatiblepolymeric matrix degrades within 90 days of curing, and about 55% orless by weight of the biocompatible polymeric matrix degrades within 120days of curing, as measured using the standard method described inExample 1

Suitable biocompatible polymeric matrices can be formed from a varietyof natural and/or synthetic materials. In certain embodiments, thebiocompatible polymeric matrix is a hydrogel. Hydrogels arewater-swellable materials formed from oligomeric or polymeric moleculeswhich are crosslinked to form a three dimensional network. Hydrogels canbe designed to form in situ (for example, from injectable precursorswhich crosslink in vivo). As gels, these materials can exhibitproperties characteristic of both liquids (e.g., their shape can beresilient and deformable) and solids (e.g., their shape can be discreteenough to maintain three dimensions on a two dimensional surface).

The crosslinkable biomaterial can be designed to rapidly cure in situupon injection. In some embodiments, the crosslinkable biomaterial has acure time, as measured using the standard method described in Example 1,of less than about 20 minutes (e.g., less than about 15 minutes, lessthan about 10 minutes, less than about 5 minutes, less than about 3minutes, or less than about 1 minute).

The crosslinkable biomaterial injected into the LAA can have a lowviscosity relative to the biocompatible polymeric matrix. This can allowthe crosslinkable biomaterial to be readily injected, for example, via ahand-powered delivery device such as a syringe. This can provide aphysician with a large degree of control over the flow rate of thecrosslinkable biomaterial during injection, and allow the flow to bealtered or stopped, as required, during the course of injection. Therelatively low viscosity of the crosslinkable biomaterial relative tothe biocompatible polymeric matrix also can allow the crosslinkablebiomaterial to conform to the shape of the LAA prior to curing.

For example, in some embodiments, the crosslinkable biomaterial injectedinto the LAA has a viscosity of about 1,000 cP or less (e.g., about 900cP or less, about 800 cP or less, about 750 cP or less, about 700 cP orless, about 600 cP or less, about 500 cP or less, about 400 cP or less,about 300 cP or less, about 250 cP or less, about 200 cP or less, about150 cP or less, about 100 cP or less, or. about 50 cP or less). Incertain cases, the crosslinkable biomaterial injected into the LAA has aviscosity of at least 1 cP (e.g., at least 2 cP, at least 2.5 cP, atleast 5 cP, or at least 10 cP). The crosslinkable biomaterial can have aviscosity ranging from any of the minimum values described above to anyof the maximum values described above.

In some embodiments, the crosslinkable biomaterial comprises amulticomponent composition which crosslinks in situ to form abiocompatible polymeric matrix. For example, the crosslinkablebiomaterial can comprise a first precursor molecule and a secondprecursor molecule. “Precursor molecule”, as used herein, generallyrefers to a molecule present in the crosslinkable biomaterial whichinteracts with (e.g., crosslinks with) other precursor molecules of thesame or different chemical composition in the crosslinkable biomaterialto form a biocompatible polymeric matrix. Precursor molecules caninclude monomers, oligomers and polymers which can be crosslinkedcovalently and/or non-covalently.

The multiple components of the composition (e.g., the first precursormolecule and the second precursor molecule) can be combined prior toinjection, can be present in two or more separate solutions which arecombined during the injection (e.g., by mixing within a delivery deviceused to inject the material), or can be present in two or more separatesolutions which are individually injected into the LAA.

In some embodiments, the crosslinkable biomaterial comprises a firstprecursor molecule present in a first solution and a second precursormolecule present in a second solution. In one embodiment, the twosolutions are combined during the course of injection (e.g., by mixingwithin a delivery device used to inject the material). In anotherembodiment, the two solutions are individually injected into the LAA,and combine in situ. In these cases, the two solutions can be injectedsimultaneously or sequentially. Depending on the mechanism ofcrosslinking, an accelerator (e.g., a pH modifying agent or radicalinitiator) can be added and/or an external stimulus (e.g., UVirradiation) can be applied to ensure uniform and rapid curing of thecrosslinkable biomaterial to form a biocompatible matrix. In cases wherean accelerator is added, the accelerator can be incorporated into one ormore of the solutions containing a precursor molecule prior toinjection. The accelerator can also be present in a solution which doesnot contain a precursor molecule. This accelerator solution can then beinjected simultaneously or sequentially with one or more solutionscontaining one or more precursor compounds to initiate formation of thebiocompatible polymeric matrix.

Suitable precursor molecules can be selected in view of the desiredproperties of the crosslinkable biomaterial and resultant biocompatiblepolymeric matrix. In some cases, the crosslinkable biomaterial comprisesone or more oligomeric or polymeric precursor molecules. For example,precursor molecules can include, but are not limited to, polyetherderivatives, such as poly(alkylene oxide)s or derivatives thereof,polysaccharides, peptides, and polypeptides, poly(vinyl pyrrolidinone)(“PVP”), poly(amino acids), and copolymers thereof.

The precursor molecules can further comprise one or more reactivegroups. Reactive groups are chemical moieties in a precursor moleculewhich are reactive with a moiety (such as a reactive group) present inanother precursor molecule to form one or more covalent and/ornon-covalent bonds. Examples of suitable reactive groups include, butare not limited to, active esters, active carbonates, aldehydes,isocyanates, isothiocyanates, epoxides, alcohols, amines, thiols,maleimides, groups containing one or more unsaturaturated C—C bonds(e.g., alkynes, vinyl groups, vinylsulfones, acryl groups, methacrylgroups, etc.), azides, hydrazides, dithiopyridines, N-succinimidyl, andiodoacetamides. Suitable reactive groups can be incorporated inprecursor molecules to provide for crosslinking of the precursormolecules.

In some embodiments, one or more of the precursor molecules comprises apoly(alkylene oxide)-based oligomer or polymer. Poly(alkyleneoxide)-based oligomer and polymers are known in the art, and includepolyethylene glycol (“PEG”), polypropylene oxide (“PPO”), polyethyleneoxide-co-polypropylene oxide (“PEO-PPO”), co-polyethylene oxide block orrandom copolymers, poloxamers, meroxapols, poloxamines, and polyvinylalcohol (“PVA”). Block copolymers or homopolymers (when A=B) may belinear (AB, ABA, ABABA or ABCBA type), star (A_(n)B or BA_(n)C, where Bis at least n-valent, and n is an integer of from 3 to 6) or branched(multiple A's depending from one B). In certain embodiments, thepoly(alkylene oxide)-based oligomer or polymer comprises PEG, a PEO-PPOblock copolymer, or combinations thereof.

In some embodiments, one or more of the precursor molecules is definedby Formula I or Formula II

wherein

W is a branch point;

A is a reactive group (e.g., a nucleophilic group or a conjugatedunsaturated group);

m and n are integers of from 1 to 500 (e.g., an integers of from 1 to200); and

j is an integer greater than 2 (e.g., an integer of from 2 to 8).

In some embodiments, one or more of the precursor molecules comprises abiomacromolecule. The biomacromolecule can be, for example, a protein(e.g., collagen) or a polysaccharide. Examples of suitablepolysaccharides include cellulose and derivatives thereof, dextran andderivatives thereof, hyaluronic acid and derivatives thereof, chitosanand derivatives thereof, alginates and derivatives thereof, and starchor derivatives thereof. Polysaccharides can derivatized by methods knownin art. For example, the polysaccharide backbone can be modified toinfluence polysaccharide solubility, hydrophobicity/hydrophilicity, andthe properties of the resultant biocompatible polymeric matrix formedfrom the polysaccharide (e.g., matrix degradation time). In certainembodiments, one or more of the precursor molecules comprises abiomacromolecule (e.g., a polysaccharide) which is substituted by two ormore (e.g., from about 2 to about 100, from about 2 to about 25, or fromabout 2 to about 15) reactive groups (e.g., a nucleophilic group or aconjugated unsaturated group).

In some cases, the crosslinkable biomaterial can comprise a firstprecursor molecule which comprises an oligomer or polymer having one ormore first reactive groups, each first reactive group comprising one ormore pi bonds, and a second precursor molecule comprises an oligomer orpolymer having one or more second reactive groups, each second reactivegroup comprising one or more pi bonds. The first reactive group can bereactive (e.g., via a Click chemistry reaction) with the second reactivegroup, so as to form a covalent bond between the first precursormolecule and the second precursor molecule. For example, the firstreactive group and the second reactive group undergo a cycloadditionreaction, such as a [3+2] cycloaddition (e.g., a Huisgen-type1,3-dipolar cycloaddition between an alkyne and an azide) or aDiels-Alder reaction.

In some cases, the crosslinkable biomaterial can comprise a firstprecursor molecule which comprises an oligomer or polymer having one ormore nucleophilic groups (e.g. amino groups, thiol groups hydroxygroups, or combinations thereof), and a second precursor molecule whichcomprises an oligomer or polymer having one or more conjugatedunsaturated groups (e.g., vinyl sulfone groups, acryl groups, orcombinations thereof). In such cases, the first precursor molecule andthe second precursor molecule can react via a Michael-type additionreaction. Suitable conjugated unsaturated groups are known in the art,and include those moieties described in, for example, U.S. PatentApplication Publication No. US 2008/0253987 to Rehor, et al., which isincorporated herein by reference in its entirety.

In certain embodiments, the crosslinkable biomaterial can comprise afirst precursor molecule and a second precursor molecule. The firstprecursor molecule comprises a poly(alkylene oxide)-based oligomer orpolymer having x nucleophilic groups, wherein x is an integer greaterthan or equal to 2 (e.g., an integer of from 2 to 8, or an integer offrom 2 to 6). The poly(alkylene oxide)-based polymer can comprise, forexample, poly(ethylene glycol). The nucleophilic groups can be selectedfrom the group consisting of sulfhydryl groups and amino groups. Thefirst precursor molecule can have a molecular weight of from about 1 kDato about 10 kDa (e.g., from about 1 kDa to about 5 kDa). In someembodiments, the first precursor molecule comprises pentaerythritolpoly(ethylene glycol)ether tetrasulfhydryl.

The second precursor molecule can comprises a biomacromolecule having yconjugated unsaturated groups, wherein y is an integer greater than orequal to 2 (e.g., an integer of from 2 to 100, or an integer of from 2to 25). The biomacromolecule can comprise a polysaccharide, such asdextran, hyaluronic acid, chitosan, alginate, or derivatives thereof.The conjugated unsaturated groups can be selected from the groupconsisting of vinyl sulfone groups and acryl groups. The secondprecursor molecule can have a molecular weight of from about 2 kDa toabout 250 kDa (e.g., from about 5 kDa to about 50 kDa). In someembodiments, the second precursor molecule comprises dextran vinylsulfone.

In some embodiments, the in situ crosslinking of the precursor moleculestakes place under basic conditions. In these embodiments, thecrosslinkable biomaterial can further include a base to activate thecrosslinking of the precursor molecules. A variety of bases comply withthe requirements of catalyzing, for example, Michael addition reactionsunder physiological conditions without being detrimental to thepatient's body. Suitable bases include, but are not limited to, tertiaryalkyl-amines, such as tributylamine, triethylamine,ethyldiisopropylamine, or N,N-dimethylbutylamine. For a givencomposition (and mainly dependent on the type of precursor molecules),the gelation time can be dependant on the type of base and of the pH ofthe solution. Thus, the gelation time of the composition can becontrolled and adjusted to the desired application by varying the pH ofthe basic solution.

In a some embodiments, the base, as the activator of the covalentcrosslinking reaction, is selected from aqueous buffer solutions whichhave their pH and pK value in the same range. The pK range can bebetween 9 and 13. Suitable buffers include, but are not limited to,sodium carbonate, sodium borate and glycine. In one embodiment, the baseis sodium carbonate.

The crosslinkable biomaterial can further contain organic and/orinorganic additives, such as thixotropic agents, stabilizers forstabilization of the precursor molecules in order to avoid prematurecrosslinking, and/or fillers which can result in an increase orimprovement in the mechanical properties (e.g., cohesive strength and/orelastic modulus) of the resultant biocompatible matrix. Examples ofstabilizing agents include radical scavengers, such as butylatedhydroxytoluene or dithiothreitol.

In some embodiments, a bioactive agent can be incorporated into thecrosslinkable biomaterial (and thus into the resultant biocompatiblepolymer matrix). The bioactive agent can be a therapeutic agent,prophylactic agent, diagnostic agent, or combinations thereof. In somecases, the crosslinkable biomaterial (and thus the resultantbiocompatible polymer matrix) comprises an agent that promotesinfiltration of cells onto or into the biocompatible polymeric matrix.For example, the agent can be an agent that promotes endothelialization.Promoting endothelialization refers to promoting, enhancing,facilitating, or otherwise increasing the attachment of, and growth of,endothelial cells on a surface of the biocompatible polymeric matrix.Examples of suitable agents that promote endothelialization are known inthe art, and include growth factors (e.g., VEGF, PDGF, FGF, PlGF andcombinations thereof), extracellular matrix proteins (e.g., collagen),and fibrin. In some cases, the crosslinkable biomaterial (and thus theresultant biocompatible polymer matrix) comprises an anticoagulant, suchas warfarin or heparin. In these cases, the anticoagulant can be locallydelivered by elution from the resultant biocompatible polymer matrix. Insome cases, the crosslinkable biomaterial (and thus the resultantbiocompatible polymer matrix) comprises a contrast agent, such as gold,platinum, tantalum, bismuth, or combinations thereof to facilitateimaging of the crosslinkable biomaterial (e.g., during injection) or theresultant biocompatible polymer matrix (e.g., to confirm completeocclusion of the LAA or monitor degradation of the biocompatible polymermatrix).

The crosslinkable biomaterial can be injected into the LAApercutaneously. In some embodiments, the crosslinkable biomaterial canbe percutaneously injected via a delivery catheter. The particularcomponents and features of the deliver catheter can vary based on anumber of factors, including the nature of the crosslinkable biomaterialto be delivered. For example, the number of lumens in the deliverycatheter and/or the presence or absence of a mixing channel can beselected in view of the identity of the precursor molecule(s) and/or themechanism by which the biomaterial crosslinks.

An example delivery catheter is illustrated in FIG. 2. The deliverycatheter (200) can comprise a proximal region (202), a distal region(204) comprising a distal tip (206), at least a first lumen (210)extending from the proximal region (202) to the distal region (204), andan occluding element (208) positioned in proximity to the distal tip(206).

The delivery catheter can be structured to accommodate the anatomy of apatient, in terms of its dimensions (e.g., length and cross-sectionaldimensions), configurations, and operability, so as to facilitatepercutaneous delivery of the crosslinkable biomaterial to the cavity orpassageway to be occluded. For example, in the case of a deliverycatheter configured to deliver a crosslinkable biomaterial to the LAA ofa patient, the dimensions (e.g., length and cross-sectional dimensions),configurations, and operability of the delivery catheter can be designedto accommodate the vascular geometry of a patient.

The cross-sectional dimension (e.g., the diameter or thickness) of thedelivery catheter can be configured to accommodate the natural interiordimensions of vasculature of a patient, so as to permit advancement ofthe delivery catheter through the patient's vasculature to reach theLAA. In some cases, the largest cross-sectional dimension of the portionof the catheter which is configured to be advanced within the patient'svasculature is about 5.0 mm or less (e.g., about 4.7 mm or less, about4.3 mm or less, about 4.0 mm or less, about 3.7 mm or less, about 3.3 mmor less, about 3.0 mm or less, about 2.7 mm or less, about 2.3 mm orless, or about 2.0 mm or less, about 2.5 mm or less, about 2 mm orless). The largest cross-sectional dimension of the elongate member canbe at least about 1.0 mm (e.g., at least about 1.33 mm, at least about1.67 mm, at least about 2.0 mm, at least about 2.3 mm, at least or atleast about 3.0 mm) These dimensions are provided with the provisio thatthe cross-sectional dimensions and composition of the delivery areselected such that the structural integrity of the delivery catheterrequired for functionality is not substantially compromised by thecross-sectional dimensions of the delivery catheter.

The largest cross-sectional dimension of the elongate member can rangefrom any of the minimum dimensions described above to any of the maximumdimensions described above. In some embodiments, the largestcross-sectional dimension of the elongate member is from about 1.0 mm toabout 3.3 mm.

For use in methods of occluding the LAA of a patient, the deliverycatheter is generally of sufficient length to reach the LAA of a patientwhen inserted percutaneously. For example, the delivery catheter can belong enough such that when the delivery catheter is inserted into thefemoral vein of a patient, the distal tip of the delivery catheter canreach the LAA of the patient while portions of the delivery catheterproximal to the distal tip extend through the patient's vasculature to apoint outside of the patient's body. In this way, the some or all of theproximal region of the delivery catheter can remain externallyaccessible to provide a means of manipulating the delivery catheter(e.g., advancing and retracting the delivery catheter, actuating theoccluding member, etc.) and/or injecting the crosslinkable biomaterial.In certain embodiments, the delivery catheter has a length of from about80 cm to about 130 cm (e.g., from about 90 cm to about 120 cm, or fromabout 100 cm to about 110 cm).

The delivery catheter, or regions thereof, can be formed from a varietyof materials. The materials can optionally be selected such that thedelivery catheter has structural integrity sufficient to permitadvancement of the delivery catheter to the occlusion site in thepatient and permit maneuvering and operation of the delivery catheter,while also permitting yielding and bending in response to encounteredanatomical barriers and obstacles within the patient's body (e.g.,within the vasculature).

The delivery catheter can be formed from a material or combination ofmaterials, such as polymers, metals, and polymer-metal composites. Insome examples, soft durometer materials are used to form all or part ofthe delivery catheter to reduce subject patient discomfort and minimizethe risk of damage to the patient's vasculature (e.g., perforation). Insome embodiments, the delivery catheter is formed, in whole or in part,from a polymeric material. Examples of suitable plastics and polymericmaterials include, but are not limited to, silastic materials andsiliconbased polymers, polyether block amides (e.g., PEBAX®,commercially available from Arkema, Colombes, France), polyimides,polyurethanes, polyamides (e.g., Nylon 6,6), polyvinylchlorides,polyesters (e.g., HYTREL®, commercially available from DuPont,Wilmington, Del.), polyethylenes (PE), polyether ether ketone (PEEK),fluoropolymers such as polytetrafluoroethylene (PTFE), perfluoroalkoxy,fluorinated ethylene propylene, or blends and copolymers thereof.Examples of suitable metals which may form some or all of the deliverycatheter include stainless steel (e.g., 304 stainless steel), nickel andnickel alloys (e.g., nitinol or MP-35N), titanium, titanium alloys, andcobalt alloys. In certain embodiments, the delivery catheter comprisesof two different materials. Radiopaque alloys, such as platinum andtitanium alloys, may also be used to fabricate, in whole or in part, thedelivery catheter to facilitate real-time imaging during proceduresperformed using the delivery catheter.

If desired, the delivery catheter can be coated or treated with variouspolymers or other compounds in order to provide desired handling orperformance characteristics, such as to increase lubricity. In certainembodiments, the delivery catheter is coated withpolytetrafluoroethylene (PTFE) or a hydrophilic polymer coating, such aspoly(caprolactone), to enhance lubricity and impart desirable handlingcharacteristics.

The occluding element (208) can be any structure configured totransitorially occlude the LAA when positioned in proximity to theopening of the LAA. The occluding element can be configured to beretractable or inflatable, such that the occluding element can possess aretracted or un-inflated state in which it is not configured to occludethe LAA and a deployed or inflated state in which it is configured toocclude the LAA when positioned in proximity to the opening of the LAA(e.g., to fluidly isolate the LAA from the left atrium). In someembodiments, the occluding element has a cross-sectional dimension of atleast about 1.0 cm (e.g., at least about 1.25 cm, or at least about 1.5cm) when configured to occlude the LAA (e.g., when deployed orinflated).

In some embodiments, the occluding element comprises an inflatableballoon configured to substantially seal the LAA when inflated. Theinflatable balloon can be formed from any suitable fluid impermeablepolymer film, and can be configured to be either compliant ornon-compliant when inflated. Suitable polymeric materials that can beused to form the inflatable balloon include, for example, silicone,polyethylene, polyurethane, and PET. The inflatable balloon can includerib members extending longitudinally from its distal end to its proximalend which can be configured to provided structural integrity to theinflatable member and/or mechanically interlock with the trebeculae ofthe inside surface of the LAA or other surface irregularities of theinside surface of a patient's body cavity or passageway. The rib memberscan be disposed around the complete circumference of the inflatableballoon. The rib members can also be disposed around a portion of thecircumference of the inflatable balloon. The rib members can also bedisposed in a spiral configuration, or in a random orientation withrespect to one another.

The inflatable balloon can be filled with a fluid or gel which can beinjected under pressure through the delivery catheter and into theinterior of the inflatable balloon. Accordingly, referring again to FIG.2, the delivery catheter (200) can further comprise one or moreadditional lumens (e.g., one or more inflator lumens; 214) whichdistally extend from the proximal region (202), and are fluidlyconnected to the inflatable balloon. Suitable fluids to inject caninclude saline and silicone. The fluid, gel or polymer used to fill theinflatable balloon can contain contrast agents such as gold, tantalum,bismuth, barium sulfate or the like in order to improve, for example,visualization under fluoroscopy or x-ray imaging.

Referring again to FIG. 2, the occluding element (208) can positionedwithin the distal region (204) of the delivery catheter in proximity tothe distal tip (206), such that when the distal tip is advanced into theLAA of the patient, the occluding element configured to seal the openingthe LAA. For example, is some embodiments, the occluding element (208)can be positioned within about 10 mm of the distal tip (206; measured asthe distance between the distal tip and the distal end of the occludingelement) of the delivery catheter (e.g., within about 9 mm, within about8 mm, within about 7.5 mm, within about 7 mm, within about 6 mm, withinabout 5 mm, within about 4 mm, within about 3 mm, within about 2.5 mm,or within about 2 mm) In some embodiments, the distal region (204) ofthe catheter configured to be present within the left atrium can becurved to accommodate the anatomy of the LAA.

Referring again to FIG. 2, the delivery catheter (200) can furthercomprise a second lumen (212) extending from the proximal region (202)to the distal region (204). In some embodiments, the first lumen (210)can be fluidly isolated from the second lumen (212). In theseembodiments, both the first lumen (210) and the second lumen (212) canbe fluidly connected to the distal tip of the delivery catheter (206).In other embodiments, the first lumen (210) and the second lumen (212)are fluidly connected by a mixing channel (217).

The mixing channel can be configured to mix two solutions flowingthrough the first lumen and the second lumen, for example, so as to forma homogenous solution or suspension. As shown in FIG. 2, the mixingchannel (217) can comprises a proximal end (218) fluidly connected thefirst lumen (210) and the second lumen (212), a distal end (220) fluidlyconnected to the distal tip (206) of delivery catheter; and a mixer(222) fluidly connecting the proximal end (218) and the distal end(220). The mixing channel (217) can be positioned at any suitable pointalong the length of the delivery catheter. In some embodiments, themixing channel (217) is positioned within the distal region (204) of thedelivery catheter (200).

The mixer (222) can be one or more fluid channels configured to mix twosolutions flowing into the mixer from the first lumen and the secondlumen. The mixer can adopt a variety of geometries, based on for examplethe solutions to be mixed and the length of the mixer. For example, themixer can be configured to mix (e.g., to render homogeneous) twosolutions with Reynolds numbers of from 2 to 10 (e.g., from 3 to 5)which flow through the mixer. The mixer can be, for example, a channel(e.g., a serpentine or tortuous channel, or a channel containing one ormore protrusions) which induces turbulent flow so as to mix the fluids.Suitable geometries for mixers are known in the art, and somerepresentative geometries are illustrated for example in FIG. 3.

Referring again to FIG. 2, the delivery catheter (200) can furthercomprise one or more additional features. The delivery catheter (200)can further comprise one or more additional lumens (e.g., one or moreauxiliary lumens; 216) which distally extend from the proximal region(202) to the distal region (204). In some embodiments, the deliverycatheter (200) comprises an auxiliary lumen (216) that is fluidlyconnected to the distal tip (206), such that the auxiliary lumen (216)is in fluid communication with the region distal to the distal tip ofthe delivery catheter. The auxiliary lumen (216) can be configured toaccept a guidewire and/or sheath to facilitate advancement of thedelivery catheter, to accept a needle used to pierce for example thefossa ovalis to gain access to the left atrium, to accept a probe tomonitor pressures distal to the distal tip of the delivery catheter, toaccept a device, such as a fiber optic bundle (e.g., for transmitting UVlight), configured to accelerate curing of the crosslinkablebiomaterial, and/or configured to permit removal of fluid or othermaterials from the region distal to the distal tip of the deliverycatheter.

Referring again to FIG. 2, the proximal region (202) of the deliverycatheter (200) can include a manifold (224) to facilitate access to thelumens of the delivery catheter. The delivery catheter (200) can includea port for fluid connection to the one or more inflator lumens (214), aport for fluid connection to the first lumen (228), a port for fluidconnection to the second lumen (230), and/or a port for fluid connectionto the one or more auxiliary lumens (232). In some embodiments, one ormore of the ports, such as the port for fluid connection to the one ormore auxiliary lumens (232), can be connected to a branched port (e.g.,a hemostatic valve; 234) to facilitate access of the lumen by multipledevices or for multiple purposes (e.g., to advance a guidewire andmonitor pressure). The ports can be configured to form leak-freeconnections (e.g., a Luer Taper connection such as a Luer-lock orLuer-slip connection) with, for example, indeflators and syringes usedto inject fluid into the lumens or to withdraw fluid from the lumens(e.g., to actuate the occluding member, to inject the crosslinkablebiomaterial, or to remove fluid from the region distal to the distal tipof the delivery catheter).

The delivery catheter can be is inserted into the vasculature of thepatient (e.g., into the femoral vein), and advanced through thepatient's vasculature, such that the distal tip of the delivery catheterreaches the patient's left atrium. The LAA may be accessed through anyof a variety of pathways as will be apparent to those of skill in theart. Trans-septal access can be achieved by introducing the deliverycatheter into, for example, the femoral or jugular vein, andtransluminally advancing the catheter into the right atrium.Radiographic imaging (e.g., single or biplanar fluoroscopy, sonographicimaging, or combinations thereof) can be used to image the deliverycatheter during the procedure and guide the distal end of the catheterto the desired site. As a result, in some cases, at least a portion ofthe delivery catheter can be formed to be at least partially radiopaque.

Once in the right atrium, a long hollow needle with a preformed curveand a sharpened distal tip can be advanced through the auxiliary lumen,and forcibly inserted through the fossa ovalis. A radiopaque contrastmedia can be injected through the needle to allow visualization andensure placement of the needle in the left atrium, as opposed to beingin the pericardial space, aorta, or other undesired location. Once theposition of the needle in the left atrium is confirmed, the deliverycatheter can be advanced over the needle through the septum and into theleft atrium. Alternative approaches to the LAA are known in the art, andcan include venous transatrial approaches such as transvascularadvancement through the aorta and the mitral valve.

The distal tip of the delivery catheter can then be advanced into theLAA, such that the occluding element of the delivery catheter isconfigured to transitorily occlude the LAA. In some cases, the occludingelement is actuated to occlude the LAA. For example, in cases where theoccluding element comprises an inflatable balloon configured tosubstantially seal the LAA when inflated, and the balloon can beinflated when the catheter is properly positioned to seal the LAA. Insome embodiments, the balloon is inflated with a solution comprising acontrast agent to facilitate imaging and monitor occlusion.

If desired, fluid (e.g., blood) present in the LAA can be removedfollowing sealing of the LAA with the occluding element. Blood can bewithdrawn, for example, via the one or more auxiliary lumens.Optionally, the volume of blood removed from the LAA of the patient canbe measured, and used to determine an appropriate amount ofcrosslinkable biomaterial to be injected into the LAA of the patient.

The crosslinkable biomaterial can then be injected into the LAA of thepatient via the delivery catheter. In some embodiments, the total volumeof crosslinkable biomaterial injected ranges from about 2 cc to about 8cc. The crosslinkable biomaterial can be injected via one or morelumens, for example, using a syringe, inflator, or other device fluidlyconnected to the one or more lumens. In certain embodiments, thecrosslinkable biomaterial can comprise a first precursor moleculepresent in a first solution and a second precursor molecule present in asecond solution, wherein the first precursor molecule is reactive withthe second precursor molecule to form a biocompatible polymeric matrix.In these embodiments, the first solution can be injected into a firstlumen in the catheter and the second solution can be injected into asecond lumen in the catheter. In one embodiment, the two solutions arecombined during the course of injection via the delivery catheter (e.g.,by mixing within a mixing channel within the delivery catheter). Inanother embodiment, the two solutions are individually (simultaneouslyor sequentially) injected into the LAA, and combine in situ to form abiocompatible polymeric matrix. In cases when the two solutions aresimultaneously injected, the two solutions can be injected using, forexample, a dual-barrel syringe or indeflator, wherein the first barrelcontains the first solution and is fluidly connected to the first lumen,and the second barrel contains the second solution and is fluidlyconnected to the second lumen.

Upon injection into the LAA, the crosslinkable biomaterial increases inviscosity to form a biocompatible polymeric matrix. If desired, anaccelerator (e.g., a catalyst or UV light) can be supplied to increasecure rate, initiate curing, and/or ensure thorough curing of thebiocompatible polymeric matrix. The position of delivery catheter in theLAA can be maintained following injection of the crosslinkablebiomaterial, such that the occluding element is configured to seal theLAA for a period of time greater than the cure time of the crosslinkablebiomaterial. Following curing, the delivery catheter can be withdrawn.

In some embodiments, during the procedure described above, the patientcan be positioned in a posture which is effective to facilitateocclusion of the LAA. For example, the patient can be positioned at anangle relative to the ground which is effective to facilitate injectionof the crosslinkable biomaterial into the LAA of the patient. Bypositioning the patient at an angle (e.g., approximately a 30° to 40°angle relative to horizontal), gravity can assist the flow of thecrosslinkable biomaterial into the LAA, facilitating complete occlusionof the LAA.

In general, the crosslinkable biomaterial is injected to the LAApercutaneously, for example using a delivery catheter as discussedabove. Alternatively, the crosslinkable biomaterial can be introducedintraoperatively during an invasive procedure, or ancillary to anotherprocedure which gives access to the LAA.

The methods described herein can be used to occlude the LAA, thusdecreasing the risk of thromboembolic events associated with AF.

In some cases, the patient treated using the methods described hereinexhibits AF. In patients with non-rheumatic AF, the risk of stroke canbe estimated by calculating the patient's CHA₂DS₂-VASc score. A highCHA₂DS₂-VASc score corresponds to a greater risk of stroke, while a lowCHA₂DS₂-VASc score corresponds to a lower risk of stroke. In someembodiments, the patient treated using the methods described has aCHA₂DS₂-VASc score of 2 or more.

In certain embodiments, the patient is contraindicated foranticoagulation therapy. For example, the patient can have an allergy toone or more common anticoagulants (e.g. warfarin), can express apreference to not be treated with anticoagulants, can be taking anothermedication that interacts unfavorably with an anticoagulant, or can beat risk for hemorrhage.

The methods, devices, and compositions described herein can be appliedto occlude other cavities or passageways in a patient, in particularother cavities or passageways in the cardiovascular system of a patient.In certain embodiments, the methods, devices, and/or compositions orinjected or otherwise introduced into a pseudoaneurysm to occlude thepseudoaneurysm. In certain cases, the pseudoaneurysm is present in ahigh risk location for surgery (e.g., connected to the aorta or anothermajor artery). In one embodiment, the pseudoaneurysm is connected to thefemoral artery.

EXAMPLES Example 1: Synthesis and Characterization of PEG-DextranHydrogels Preparation of Hydrogel Precursor Molecules

Tetra-functional PEG-thiol (PEG4SH) (82.7% activity) was purchased fromSunbio (Anyang City, South Korea), and used for hydrogel formationwithout further purification or modification.

Dextran from Leuconostoc mesenteroides (average MW=15,000-20,000 Da),divinyl sulfone (DVS; 97%, MW=118.15 Da), and 3-mercaptopropionic acid(MW=106.14 Da) were purchased from Sigma-Aldrich (St. Louis, Mo.). Thesynthesis of dextran vinyl sulfone (DextranVS) containing an ethylspacer was performed using N,N0-dicyclohexyl-carbodiimide (DCC, FisherScientific) and 4-(dimethylamino)pyridinium 4-toluenesulfonate (DPTS) ascatalysts. DPTS was prepared using methods known in the art. Briefly,5.0 g of p-TSA monohydrate was dissolved in 100 ml THF.4-(Dimethylamino)-pyridine (DMAP, 99%) (Sigma-Aldrich, St. Louis, Mo.)at one molar equivalent to p-TSA was added to this mixture. The mixturewas subsequently filtered to isolate a precipitate which was furtherdissolved in dichloromethane (DCM, Fisher Scientific) and recrystallizedusing rotary vacuum evaporator.

Dextran vinyl sulfone ester synthesis was performed by adding 2.5 or 5.0g DVS in 90 mL of inert nitrogen saturated DMSO, followed by dropwiseaddition of 3-MPA to it under continuous stirring. The reaction wascontinued for 4 hours in the dark. Dextran was dissolved in 30 mL DMSO,and a solution of DCC and p-TSA in 30 ml DMSO was added dropwise. Thereaction mixture was stirred until a clear solution was obtained.Finally, the mixture was added to DVS/MPA solution in the dark, andreaction was allowed to proceed for 24 hours at room temperature.

After the completion of reaction, N,N-dicyclohexylurea (DCU) salt wasfiltered using a vacuum filter and the product was recovered byprecipitation in 1000 mL of ice cold 100% ethanol. The precipitate wasseparated from residual ethanol through centrifugation at 3000 rpm for15 min., followed by vacuum drying. The precipitate was re-dissolved inat least 100 mL of de-ionized water (pH adjusted to 7.8) and vortexed toobtain a clear solution. Finally, un-reacted polymer was removed viaultra-filtration using an Amicon filter (MWCO=10,000 Da, Millipore). Theresulting viscous product was lyophilized to remove water. Vinyl sulfonesubstitution was confirmed and degree of substitution (DS) wasdetermined via NMR spectroscopy.

Formation of PEG-Dextran Hydrogels

Controlled masses of PEG and dextran vinyl sulfone were mixed with acontrolled volume of TEA buffer. Two different types of dextran vinylsulfone (DS 5 and DS10) were examined. Samples were made with varyingconcentrations of hydrogel in the buffer, measured in terms of wt.%/vol. Samples ranging from 10%-40% wt./vol. were evaluated. The PEG anddextran components were mixed in a 1:1 stoichiometric ratio.

Characterization of PEG-Dextran Hydrogels

The materials properties of the PEG-Dextran hydrogels, as well assolutions of the hydrogel precursor molecules were evaluated.

Measurement of Density and Viscosity

A controlled volume (500 μL) of each sample was collected, and weighed.Knowing the mass and volume, density was calculated. The densitiesmeasured for solutions of hydrogel precursor molecules are included inTable 1.

TABLE 1 Density measurements for solutions of hydrogel precursormolecules. Table 1: Density (g/cm³) of Materials Concentration 10% 20%30% 40% Material PEG 1.080 1.202 1.295 1.393 Dextran DS 5 1.120 1.1911.305 1.395 Dextran DS 10 1.107 1.193 1.306 1.399

Samples of hydrogel components were prepared as described previously,and heated to 37° C. in a water bath. Solutions of the hydrogelprecursor molecules were also measured. Kinematic viscosities weremeasured using size 75 and size 150 Canon Manning Semi-Micro glasscapillary viscometers. Once kinematic viscosity was measured, dynamicviscosity was calculated using the following relation:

$\upsilon = \frac{\mu}{\rho}$

Where υ is kinematic viscosity, μ is dynamic viscosity, and ρ is densityof the measured material. For each sample, viscosity was measured 12times to ensure accuracy. The dynamic and kinematic viscosities ofsolutions of hydrogel precursor molecules at different concentrationsare included in Table 2.

TABLE 2 Dynamic and kinematic viscosities of solutions of hydrogelprecursor molecules. Concentration 10% 20% 30% 40% Dynamic Viscosity(cP) of Materials Material PEG 2.646 7.773 24.729 32.810 Dextran DS 51.789 3.859 7.371 11.871 Dextran DS 10 1.607 4.075 6.478 16.335Kinematic Viscosity (cStr) of Materials Material PEG 2.452 6.467 19.10023.556 Dextran DS 5 1.598 3.239 5.649 8.510 Dextran DS 10 1.451 3.4164.960 11.673

Measurement of Degradation Rate

Samples of PEG and Dextran were mixed in a 1:1 ratio and allowed tosolidify. In this study, 150 uL of each component was used. Samples wereallowed to sit for two hours to allow complete solidification. Tosimulate human body conditions, samples were then submerged in a 0.01%PBS buffer (PH 7.4), and rotated in a 37° C. incubator. Samples wereweighed at specified time intervals to gauge what percentage of materialremained. The results of the degradation trials are included in Table 3.After 90 days anywhere between 40-63% of hydrogel (by mass) haddegraded. At 120 days, anywhere between 44-95% of hydrogel by mass haddegraded

TABLE 3 Degradation results for PEG-dextran hydrogels. DS 5 DS 10 DS 5DS 10 DS 5 DS 10 Day 20% 20% 30% 30% 40% 40% Mass/Original Mass(Swelling Ratio) 0 1.00 1.00 1.00 1.00 1.00 1.00 1 1.52 1.74 3.13 3.303.32 3.73 2 2.55 2.49 3.03 3.37 3.46 5.89 8 2.63 2.68 3.43 3.09 3.704.16 15 2.28 2.52 2.62 2.85 2.86 3.41 23 2.02 2.31 2.15 2.78 2.90 3.0429 2.44 2.07 2.15 2.66 2.85 3.44 42 2.04 1.73 1.88 2.28 2.32 2.98 542.02 1.71 1.61 2.17 2.31 2.61 64 2.01 2.11 1.87 2.33 2.62 2.82 79 1.951.95 1.73 1.95 2.20 2.44 86 1.66 1.76 1.57 2.08 1.99 2.40 92 1.59 1.741.28 1.79 1.94 2.29 99 1.52 1.60 1.28 1.93 1.88 2.51 106 1.62 1.59 1.301.96 2.10 2.48 113 1.51 1.59 1.26 1.90 1.95 2.40 120 1.47 1.71 1.29 1.791.94 2.43 127 1.46 1.59 1.71 1.92 2.35 % Remaining 0 1 2 1.00 1.00 81.00 1.00 1.00 0.92 1.00 0.71 15 0.87 0.94 0.76 0.85 0.77 0.58 23 0.770.86 0.63 0.83 0.78 0.52 29 0.93 0.77 0.63 0.79 0.77 0.58 42 0.78 0.640.55 0.68 0.63 0.51 54 0.77 0.64 0.47 0.64 0.62 0.44 64 0.77 0.79 0.550.69 0.71 0.48 79 0.74 0.73 0.50 0.58 0.59 0.41 86 0.63 0.66 0.46 0.620.54 0.41 92 0.61 0.65 0.37 0.53 0.52 0.39 99 0.58 0.60 0.37 0.57 0.510.43 106 0.62 0.59 0.38 0.58 0.57 0.42 113 0.57 0.59 0.37 0.56 0.53 0.41120 0.56 0.64 0.38 0.53 0.52 0.41 127 0.56 0.59 0.00 0.51 0.52 0.40 %Degraded 0 1 2 0.00 0.00 8 0.00 0.00 0.00 0.08 0.00 0.29 15 0.13 0.060.24 0.15 0.23 0.42 23 0.23 0.14 0.37 0.17 0.22 0.48 29 0.07 0.23 0.370.21 0.23 0.42 42 0.22 0.36 0.45 0.32 0.37 0.49 54 0.23 0.36 0.53 0.360.38 0.56 64 0.23 0.21 0.45 0.31 0.29 0.52 79 0.26 0.27 0.50 0.42 0.410.59 86 0.37 0.34 0.54 0.38 0.46 0.59 92 0.39 0.35 0.63 0.47 0.48 0.6199 0.42 0.40 0.63 0.43 0.49 0.57 106 0.38 0.41 0.62 0.42 0.43 0.58 1130.43 0.41 0.63 0.44 0.47 0.59 120 0.44 0.36 0.62 0.47 0.48 0.59 127 0.440.41 1.00 0.49 0.48 0.60

Measurement of Equilibrium Swelling Ratio

Hydrogel samples were obtained and massed. The hydrogel samples werethen incubated in PBS buffer (10 mM phosphate buffered saline, e.g.,P3813-powder from Sigma yields a buffer of 0.01 M phosphate, 0.0027 Mpotassium chloride and 0.138 M sodium chloride, pH 7.4). Uponincubation, the hydrogel samples swelled, and increased mass. Every ˜168hours (7 days), the sample was removed from buffer, and massed. Theequilibrium swelling ratio, defined as:

${{equilibrium}\mspace{14mu}{swelling}\mspace{14mu}{ratio}} = \frac{w_{t}}{w_{o}}$where w_(t) is the maximum swollen weight, and w_(o) is the unswollenweight of hydrogel was determined for each hydrogel sample. Equilibriumswelling ratio was typically observe 48-72 hours after submergingsamples in PBS buffer. The equilibrium swelling ratios of each hydrogelare included in Table 4 below.

TABLE 4 Equilibrium swelling ratios of PEG-dextran hydrogels. DextranConcentration of Hydrogel Components Component 20% 30% 40% Dextran DS 52.6 3.4 3.7 Dextran DS 10 2.6 3.3 5.8

Measurement of Cure Time

The cure time of the PEG-dextran hydrogels was evaluated using a tippingvial methods. PEG and Dextran suspensions were prepared, as describedabove, at different concentrations by mixing either PEG or dextranmaterial with TEA buffer. Suspensions were mixed to a specificconcentration. Peg and dextran suspensions of equal concentrations werethen mixed in a 1:1 ratio in a sealed vial. The vial was shaken with anultrasonic shaker to ensure complete mixing. Once mixing was complete, atimer was started. The vial was continually tipped or flipped. Whenmixed components stop moving upon actuation of the vial, the hydrogel isconsidered gelled, and the timer was stopped. All hydrogels measuredexhibited curing times of 90 seconds or less.

The devices and methods of the appended claims are not limited in scopeby the specific devices, systems, kits, and methods described herein,which are intended as illustrations of a few aspects of the claims. Anydevices, systems, and methods that are functionally equivalent areintended to fall within the scope of the claims. Various modificationsof the devices, systems, kits, and methods in addition to those shownand described herein are intended to fall within the scope of theappended claims. Further, while only certain representative devices,systems, kits, and method steps disclosed herein are specificallydescribed, other combinations of the devices, systems, kits, and methodsteps also are intended to fall within the scope of the appended claims,even if not specifically recited. Thus, a combination of steps,elements, components, or constituents may be explicitly mentioned hereinor less, however, other combinations of steps, elements, components, andconstituents are included, even though not explicitly stated.

The term “comprising” and variations thereof as used herein is usedsynonymously with the term “including” and variations thereof and areopen, non-limiting terms. Although the terms “comprising” and“including” have been used herein to describe various embodiments, theterms “consisting essentially of” and “consisting of” can be used inplace of “comprising” and “including” to provide for more specificembodiments of the invention and are also disclosed. Other than wherenoted, all numbers expressing geometries, dimensions, and so forth usedin the specification and claims are to be understood at the very least,and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, to be construed in light of thenumber of significant digits and ordinary rounding approaches.

What is claimed is:
 1. A method of occluding a left atrial appendage(LAA) of a patient comprising: (a) providing a delivery cathetercomprising: a proximal region; a distal region comprising a distal tip;a first lumen extending from the proximal region to the distal region;and an occluding element positioned in proximity to the distal tip; (b)advancing the delivery catheter percutaneously through vasculature ofthe patient such that the distal tip of the delivery catheter reaches aleft atrium of the patient; (c) advancing the distal tip of the deliverycatheter into the LAA of the patient, such that the occluding elementtransitorily occludes the LAA; (d) withdrawing blood from the patient'sLAA; (e) measuring a volume of the blood withdrawn from the patient'sLAA to determine an amount of a crosslinkable biomaterial to be injectedinto the LAA of the patient; and (f) injecting the amount of thecrosslinkable biomaterial into the LAA of the patient, wherein thecrosslinkable biomaterial comprises a first precursor molecule and asecond precursor molecule; and wherein the first precursor molecule andthe second precursor molecule crosslink in situ in the LAA to form abiocompatible polymeric matrix that occupies a cavity in the LAA of thepatient, thereby preventing stagnation of blood within the cavity in theLAA of the patient.
 2. The method of claim 1, wherein the firstprecursor molecule comprises an oligomer or polymer having one or morenucleophilic groups, and the second precursor molecule comprises anoligomer or polymer having one or more conjugated unsaturated groups. 3.The method of claim 2, wherein the first precursor molecule comprises apoly(alkylene oxide)-based oligomer or polymer having x nucleophilicgroups, wherein x is an integer of from 2 to
 6. 4. The method of claim3, wherein the first precursor molecule comprises pentaerythritolpoly(ethylene glycol)ether tetrasulfhydryl.
 5. The method of claim 2,wherein the second precursor molecule comprises a biomacromoleculehaving y conjugated unsaturated groups, wherein y is an integer of from2 to
 25. 6. The method of claim 5, wherein the second precursor moleculecomprises dextran vinyl sulfone.
 7. The method of claim 1, wherein thecrosslinkable biomaterial has a cure time of less than about 5 minutes.8. The method of claim 1, wherein the biocompatible polymeric matrix hasa degradation rate such that about 70% or less by weight of thebiocompatible polymeric matrix degrades within 90 days of curing.
 9. Themethod of claim 1, wherein the biocompatible polymeric matrix exhibitsan equilibrium swelling ratio of from about 2 to about
 8. 10. The methodof claim 1, wherein the biocompatible polymeric matrix has an elasticmodulus of from about 8 kPa to about 12 kPa.
 11. The method of claim 1,wherein the occluding element comprises an inflatable balloon configuredto substantially seal the LAA when inflated.
 12. The method of claim 11,wherein step (b) comprises (i) advancing the distal tip of the deliverycatheter into the LAA, and (ii) inflating the balloon to seal the LAA.13. The method of claim 1, wherein the patient has a CHA₂DS₂-VASc scoreof 2 or more.
 14. The method of claim 1, wherein the patient iscontraindicated for anticoagulation therapy.
 15. The method of claim 1,wherein the crosslinkable biomaterial has a cure time, and wherein themethod further comprises maintaining the delivery catheter in the LAAfollowing injection of the crosslinkable biomaterial, such that theoccluding element is configured to seal the LAA for a period of timegreater than the cure time of the crosslinkable biomaterial.
 16. Themethod of claim 1, further comprising positioning the patient at anangle relative to the ground which is effective to facilitate injectionof the crosslinkable biomaterial into the LAA of the patient.
 17. Themethod of claim 1, wherein the biocompatible polymeric matrix reachesequilibrium swelling within about 24 hours.
 18. The method of claim 1,wherein the biocompatible polymeric matrix has a cure time of less thanabout 20 minutes.
 19. The method of claim 1, wherein step (f) comprisesinjecting from about 2 cc to about 8 cc of the crosslinkable biomaterialinto the LAA of the patient.
 20. The method of claim 1, wherein thebiocompatible polymeric matrix is not biodegradable.